Electrical reproducer



Feb- 18,' 1930. Y H, C, HARRISON 1,747,829

ELECTRICAL REPRODUCER Filed May l5, 192? l/r/. A/.

Patented Feb.- 182 1930 uNiTED vsTlxlEs PAT-ENT ori-ica HENRY C. HARRISON, OF PORT WASHINGTON, NEW YORK, ASSIGNOR TO BELL TELE- PHONE LABORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION 0F NEW YORK Application led May 13,

This invention relates `to vibrating Systems for acoustical apparatus and more particularly to electrical reproducers for phonogra hs. l, y

- .T e object of this invention is to provide this invention, there is provided a structure in Whichsthe vibrating system is sufficiently light and flexible to respond faithfully to allv frequencies of the audible range and dampving'means is provided which willV effectually limit the response over' the frequency range to be reproduced to a substantially straight line characteristic.

In one practical application of the'invention there is provided a bi-polar magnet system, the electromagnets of which are located within a chamber filled or substantiallyiflled with viscous matter and closed by means of avery thin flexible diaphragm which' is separated from thespool heads of lthe electromagnets by-,sucha distance that the movement of the diaphragm in response to the movement of the stylus will cause a lateral movement or flow of the viscous matter'between Aphragm and maintain it constant over the devsired range v of frequencies.

the diaphragm and spool heads that will effectually dampen the response. of' the dia- The diaphragm may be of magneticA material or carry magnetic material or both, so that its movement will vary the flux through the magnet system.

In the drawings illustrating, Fig. 1 is a view in side elevationwith parts in section of a phonograph reproducen embodying this invention; v l

Fig. 2 is a plan view of the drive-shown inFig.1;'-` ff Fig. 3 is a detail view of the pole piece and x"magnete constrlrction off the electromagnet ELEc'rnIcAL BEPRODUCER' 1927. Serial No. 191,012.

Fig. 4'i's a detail view of the electromagnet assembly showing also the diaphramland armature stylus mounting; and

F ig. 5 is an end view of the electromagnet assembly.

As shown in the drawings and particularly Fig. 1, 5 designates a U-shaped permanent magnet comprising legs 6 and 7. Abutting the leg 6 of the permanent rmagnet 5 4is an annular member 8 of magneticimfaterial provided with a threaded chamber 9 to receive a cylindrical block 1()E of o magnetic material. The blfock 1Q is bored to receivea cylindricalA part 11 of magnetic material which is adjustably supported in the bore of the block 10 bya set screw 12 and extends upwardly therefromto provide a support-for laminated pole pieces'15 and 16 carrying windings 17 and 18 supported between u' perand lower spool heads 19 and 20, and 1 and 22 respectively.

The block 10 is provided with a reduced annular'extension threaded to receive a cup shaped member or container 25 of brass or` other non-magnetic materla-lwhlch surrounds the softl iron pole pieces 15 and 16 andthe windings 17 and l8.` The container 25 is provided at its open end with an annular extension 26.to seata thin flexible diaphragm 27 preferably of magnetic material.

Abutting the end of the leg 7 of the U- shaped permanent magnet is an annular member 30 of magnetic material and having an L cross section which is adapted to fit over and'be supported by the upper-end of thecontainer 25. The projecting portion of the annular member 30 which ts over the container 25 is provided with internal threads adapted to be engaged by an externally threaded rmg 32 to draw the annular member 30 firmly against the upper end of the container 25.

' sides of the diaphragm 426 at' the portion of its periphery where it is clamped to provide a a body'portion 38 provided with arms 39 an l diaphragm 26 I is an Ring gaskets 35 and 36--are placed upon both 40 extending at right angles to the body porl tion 38 and substantial? across the diameter ofthe. free' portion: o

The body portion 38 of the armature is drilled to receive a stylus 45`which is secured therein by means of a setscrew 4.6.

The inner face of the body portion 38 and arms 39 and 40 of the amature lie fiat against the adjacent face of the diaphragm 26 and are preferably. integrally secured thereto. Thearms 39 and 40 extend along the axis of rotation of the armature and stylus 45 thereby laterallyA between the inner face of the diaphragm and the adjacent end of the electro-` magnet or spool heads 19 and 21, and serve to dampen the vibrations ofthe system to insure an equal response to all vibrational fre-.

'quencies within the audible range.

A viscous luid which is quite insensitive to normal temperature changes is one composed of 7 5% polymerized castor oil and 25% ntro-ben'zol. i

The device as illustrated and described is obviously adapted to be used as a recorder magnet, and viscous matter substantially fill- ,ing the chamber and adapted for lateral movement between the diaphragm and adjacent ends of the electromagnet in response to the movement of the diaphragm to dampen vthe vibrational movement of the diaphragm.

4. In an electrical reproducer, in combination, a chamber, a bipolar electromagnet comprising cores and spooled windings located within the chamber, a stylus operated thin magnetic diaphragm closing s'aid chamber and viscous matter ,within the chamber adapted for lateral movement between the diaphragm and the adjacent end of the electromagnet to Adampen the vibrational movement of the diaphragm.

In witness whereof, I hereunto subscribe my name this 12th day of May, A. D. 1927. r HENRY C. HARRISON.

for cutting a'sound groove upon a record or as a reproducer for generating electrical impulses 1n accordance with the movement of a stylus needle in a record groove.

The ends of legs 6 and 7 of the permanent magnet 5 a're ground to fit the annular magneticmembers 8 and'30 and the parts may be secured in position by sweating or by suitable clamping means not shown.

'What is claimed is: Y

1. An electrical reproducer comprising a magnet system includingan electromagnet, a

chamber containing the electromagnet, a .Y stylusoperated exible member closing theV chamber adjacent one end of the electromagnet, and viscous means 1n sald chamber co-` operating with the diaphragm and the electromagnet to insure an equal response by the system to all vibrational frequencies Within Q the audible range. v

2. An electrical reproducer comprising a magnet system includlng an electromagnet, a chamber containing said electroma net, a stylus operated diaphragm closing sai cham# ber, and viscous matter .in said chamber adapted for lateral Vmovement between the' diaphragm and the free end of the electromagnet to dampen the movementof said diaphragm.

3. In an electrical reproducer, in combination2 a chamber,a bipolar electromagnet com; prlsmgcores and spooled windings thereon, located within the'chamber, a iexible stylus operated diaphragm located at one end of said chamber infoperative relation to the electro- 

